Abstract: :
Purpose: In the United States, the companion pet populationincludes over 62 million dogs of which nearly 1 in 160 dogsare estimated to be diabetic. Diabetic dogs rapidly form bilateralsugar cataracts which result in vision loss. This generallyoccurs within 5–6 months from the time of diagnosis. Ithas been established that sugar cataracts in dogs are osmoticin nature and initiated by aldose reductase. The purpose ofthis study was to determine whether topical administration ofa novel aldose reductase inhibitor formulation can amelioratecanine sugar cataract formation.Methods: Ten 6–month old beagles were fed a diet containing30% galactose for a period of 7 months to induce sugar cataractformation. Six dogs were topically administered drug twice dailywhile 4 dogs were only administered vehicle. Cataract formationwas monitored at ca. 4 week intervals by portable slit lampand lens changes were documented by portable fundus photographyat 0, 3.5 and 7 months. At the termination of the study, alllenses were removed and analysed for opacity formation, galactitollevels, and drug levels.Results: All vehicle–treated dogs formed cataracts withmature to hypermature bilateral cataracts present after 7 monthsof galactose–feeding. In the topically drug treated dogs,the initial drug formulation had no effect on arresting eitherthe initiation or progression of sugar cataracts and no differencebetween the vehicle and treated dogs was apparent after 4.5months of treatment. Tapetal reflex was absent in the majorityof dogs indicating lens opacities were sufficient to block lightfrom reaching the retina. After approximately 4.5 months ofgalactose feeding, a new formulation, Kinostat, was applied.This resulted not only in a significant arrest of further cataractformation, but also, in a partial reversal of lens opacitiesand the restoration of tapetal reflex.Conclusions: Topical adminstration of a novel aldose reductaseinhibitor formulation, Kinostat, not only arrests the progressionof sugar cataracts but also reduces the density of early corticalcataracts. This suggests that functional vision can be restoredin dogs with early stages of cataract.